Alexander Nix, former chief executive of Cambridge Analytica, before a parliamentary hearing in London on Wednesday. “I’m sitting here and being subjected to frankly ridiculous accusations based on the most tenuous connections that simply aren’t supported by evidence,” he told lawmakers.CreditCreditTolga Akmen/Agence France-Presse — Getty Images

LONDON — Mark Zuckerberg, Facebook’s chief executive, has struck a conciliatory tone in the wake of a data-privacy scandal. That was not the case on Wednesday for the former chief executive of Cambridge Analytica, a consulting firm at the center of the controversy.

Alexander Nix, who led Cambridge Analytica until it suspended him in March, defiantly shot back at accusations from British lawmakers that he or his company engaged in unethical business practices, abused information pulled from the social network or played a role in the British vote to leave the European Union.

In a contentious hearing before Parliament’s media committee, Mr. Nix said Cambridge Analytica did at one point have data on millions of Facebook users. The data was harvested from the social network without the users’ consent. But, he said, Cambridge Analytica didn’t find the information useful and deleted it after a request from Facebook.

His comments contradicted evidence presented by a former Cambridge Analytica employee, Christopher Wylie, who has said the data was central to Cambridge Analytica’s political consulting work for Donald J. Trump’s 2016 presidential campaign. Mr. Wylie has also suggested that Cambridge Analytica did advising work for the Brexit vote.

Mr. Nix criticized Mr. Wylie as a “bitter and jealous” former employee bent on sabotaging the company in order to start a rival business.

“I’m sitting here and being subjected to frankly ridiculous accusations based on the most tenuous connections that simply aren’t supported by evidence,” Mr. Nix said when denying that Cambridge Analytica had worked for campaigns in favor of leaving the European Union.

“You’re building a conspiracy,” he said at another point.

The hearing was the first chance British authorities had to question Mr. Nix since The New York Times and The Observer in Britain reported in March that Cambridge Analytica had harvested the personal information of tens of millions of Facebook users without their consent. Mr. Nix said Wednesday that he had misspoken in February when he told lawmakers in London that his company had not used information collected from the social network.

Cambridge Analytica, backed by Stephen K. Bannon, the former White House political adviser, and Robert Mercer, the hedge fund billionaire, used Facebook data to create psychographic modeling techniques to target voters. While former employees have said Facebook information was critical to building products that Cambridge Analytica deployed in the 2014 and 2016 American elections, Mr. Nix played down the importance. He said the company had gotten data from many sources, including Acxiom, Experian and Infogroup.

Beyond that, Mr. Nix largely declined to speak about the Cambridge Analytica-Facebook controversy, citing a continuing investigation by Britain’s data protection authority, the Information Commissioner’s Office. The lawmakers did not press him about the company’s work with the Trump campaign.

The revelations about Cambridge Analytica have led to a global reckoning about the information Facebook has amassed on its roughly two billion users, and the ways that information can be manipulated to sway voters and tailor advertisements to specific types of people.

Mr. Zuckerberg was called to testify before American and European lawmakers to answer questions about the scandal, and the social media company has made changes to its privacy policies to limit how it collects and shares user data.

“You’ve attempted to paint yourself as the victim,” one member of Parliament said. “You’re not the victim.”

Mr. Nix shot back: “What if I was the victim?”

He said Cambridge Analytica was a convenient target for those angry about Mr. Trump’s victory and the Brexit result.

“We were simply the guys who were perceived to have contributed,” Mr. Nix said.

He saved some of his sharpest remarks for Mr. Wylie. “It’s funny how all your evidence circles all back to one individual,” Mr. Nix said.

Mr. Nix has also faced questions about Cambridge Analytica’s work in other campaigns. Channel 4 News in Britain recordedMr. Nixsuggesting methods to entrap a client’s opponent, like sending an attractive woman to seduce the rival candidate and secretly videotaping the encounter, or getting another person to propose a bribe.

Mr. Nix apologized to lawmakers on Wednesday, but also said he was the victim of an “entrapment sting” by the television network. Channel 4 defended its reporting in a statement.

New questions are now being raised about whether Mr. Nix tried to remove money from Cambridge Analytica as the damaging news reports were being published. The Financial Times reported on Wednesday that Mr. Nix had withdrawn more than $8 million from company accounts when he discovered journalists were working on articles that would soon be published, and before the company was eventually forced to file for bankruptcy protection.

Mr. Nix told lawmakers that the report wasn’t accurate. When pressed about the payment again later, he declined to comment and said he had to review the matter with his lawyer.

The months of news reports have made Mr. Nix the face of a broader debate over how social media platforms can be gamed to win votes, and whether they must be more tightly regulated.

In addition to the Parliament inquiry, the Information Commissioner’s Office is expected to publish a damning report on Cambridge Analytica this month.

A version of this article appears in print on , on Page B3 of the New York edition with the headline: Ex-Chief of Cambridge Analytica Is Testy in British Hearing. Order Reprints | Today’s Paper | Subscribe